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Re: Arc length vs pwr
10/25/96
R. Hull wrote:
>It is very easy to measure charge at a great distance with an
>electrometer using an isolated isotropic capacitance. This is how
>electric field strengths are effectively measured. The crucial point
>is that the meter must read only the scalar value of voltage.
Would you elaborate on "scalar value of voltage"? Isn't an electric
field a vector? What are the other value(s) of voltage?
>This is achieved through the nominal Teraohm input impedance of the
>avearge professional electrometer. I have an old Cary vibrating reed
>electrometer with saphire input terminals and gold chambers, and have
>charged a 20pf vacuum capacitor to 300 volts and left it for two days
>and the thing still read 300 volts! The 100% mechanical electrostatic
>voltmeters are only about 1/100th as sensitive as an electrometer, but
>still they are about 1000 times more sensitive than a good precision
>FET VOM or FET digital input meter.
>
>Richard Hull, TCBOR
>
Richard,
Last week I bought a Model 341 Weston A-C & D-C Voltmeter at a hamfest
for $15. It is a magnetically sheilded electrodynamometer and indicates
absolute volts. In a field of five orsteds it only has a 0.4% fs
deviation. I don't know much about this type of meter, but could it be
used in TC experimentation because of it's magnetic sheilding ability?
Thanks
RWW